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As a high-quality energy and chemical raw material, natural gas has attracted more and more attention. Developed countries such as the United States and Europe, which have higher levels of industrialization, have started research on natural gas metrology technologies earlier. They have invested more capital and scientific and technological strength, and have paid particular attention to the measurement of trade natural gas. From the selection of flowmeters, Europe mainly uses turbines and waistwheel flowmeters. For example, the use of turbines and waistwheel flowmeters in the Netherlands accounts for about 80%. The use of turbine flowmeters in Canada accounts for about 90%, while in the United States, it is used. Orifice-based, accounting for about 80%. On the whole, in the use of flowmeters, the climax of orifice plates was formed in the 1970s, and the use of turbine flowmeters was formed in the 1980s. In the mid- to late-1990s, an upsurge of ultrasonic flowmeters began.
In terms of traffic standards, traffic workers in various countries have spent a lot of time and have made arduous efforts. Based on the analysis and summarization of a large number of experimental and application data, they have successively introduced representative standards such as natural gas flow standard orifice measurement standards (AGA). No.3), Gas Turbine Flowmeter Standard (AGA No.7), Compressibility and Hypercompressibility of Natural Gas and Other Hydrocarbon Gases (AGA No.8), Natural Gas Standard Measurement Using Gas Ultrasonic Flowmeter (AGA No.3) 9) Use the differential pressure device to measure the fluid flow standard (ISO5167), the gas turbine flowmeter standard (ISO9951), the gas ultrasonic flowmeter standard (ISO/TR12765), and the natural gas compression factor calculation standard (ISO/DIS12213), etc. These standard procedures It has positive guiding significance for natural gas flow metering.
At the same time, people in foreign countries have gradually shifted their emphasis on the dry-border method to the thinking mode of real-flow testing—a focus on value tracking and quantitative transmission. Many real-flow testing laboratories have appeared one after another, such as the Colorado Engineering Laboratory (CEESI). ), SWRI, NMI, TCC, Pigsar, NEL, NRLM.
In recent years, the OMIL Gas Measurement Sub-Committee drafted the international recommendation PREN1776, "Basic Requirements for Natural Gas Metering System", and specified in more detail the composition of natural gas metering systems and the specific requirements for auxiliary equipment. The design principles and design guidelines for natural gas metering systems, and the on-line verification, installation, operation, and maintenance of metering systems are regulated.
China's natural gas measurement began later, and gas reservoirs are mainly distributed in Sichuan, Changqing, and Xinjiang. The use of instrumentation mainly uses orifice plates, accounting for about 88% of the total. Geometry verification is used. Since the 1970s, China has made reference to foreign series of standards, combined with its actual conditions, and made corresponding work in the aspects of design selection, use, installation, maintenance, management, and temperament analysis of natural gas meters, and reached some important conclusions. At the same time, it also explored some mature experiences in the field of resistance components and complex working conditions. In the standard aspect, the “Standard Orifice Measurement Method for Natural Gas Flow†(SY/T6143-1996) standard was formed, and equivalent use of ISO5167 formed GB2624. Bottom line, but on the overall level, there is still a significant gap with foreign countries. In recent years, the new progress of China's natural gas metrology technology
The metering technology of orifice plate throttling device and secondary instrument dual bellows differential pressure meter widely used in our country, due to its inherent defects, such as the continuous wear and corrosion of the orifice plate in the process of use; the combination of field resistance components is far more than The seven conditions stipulated in the standard; influencing factors of vortex flow and pulsating flow in the field are complex; poor adaptability to conditions with large fluctuations in gas volume and high frequency of change; lead-pressure tubes are prone to cause signal lag, etc. [1] and their measurement accuracy cannot be guaranteed. Brought new research topics to the traffic worker. In recent years, China's natural gas metrology technology has made some new advances.
lã€Intelligent secondary instrument of orifice plate throttling device
Since 1998, in the area of ​​secondary instrumentation, some natural gas metering devices have been reconstructed. Field pressure sensors, temperature transmitters, and flow computers have been gradually adopted to replace the dual bellows differential pressure gauges to achieve metering automation. . The system transmitter has high accuracy and good stability. It can use its communication function to diagnose, configure and verify on-line faults. Natural gas flow meters gradually go online, intelligent, real-time measurement.
2. New Intelligent Flowmeter Applicable to Medium and Small Flows
In order to solve some of the site's special problems of small fluctuations in flow rate and medium and low pressure, and the poor accuracy of orifice plate measurement, the domestic introduction of intelligent swirl vortex flowmeter, intelligent turbine flowmeter, which can collect pressure online , temperature, working flow, calibration flow, real-time correction of compression factor and automatic temperature and pressure compensation. After real flow calibration and application on a large scale in the field (such as Sichuan, Xinjiang, Dagang, Daqing, etc.), the effect is better. Recently, this type of dual-probe intelligent flow meter has emerged, and the anti-interference ability is further enhanced.
3. High Pressure Large Flow Measurement Technology Research xxxx With the rapid development of foreign gas ultrasonic flowmeters, China has tracked foreign advanced measurement technologies in a timely manner. Since 1999, the National Natural Gas Flow Substation (hereinafter referred to as “Measurement Pointsâ€) The station took the lead and conducted real-flow tests on representative gas ultrasonic flowmeters produced by Daniel in the United States, Instromet in the Netherlands, and Contronlotron in the United States to study ideal installation conditions, non-ideal installation conditions, installation conditions at different rotation angles, and pressure replacement. Ultrasound transducers, different pressure conditions, channel fault conditions and field applications. It is concluded that important conclusions such as real-flow verification and periodic inspection are still required after the gas ultrasonic flowmeter is dry-typed [2]. After the natural gas flow test, Beijing, Daqing, Xinjiang, Sichuan, Tianjin, and Hebei have gradually introduced about 40 sets of gas ultrasonic flowmeters. The caliber is between DN150mm-DN400mm and the uncertainty is 0.5%-1.0%. 4. Development of Real Flow Verification Technology
In the past, the standard orifice plate always used the “geometry test methodâ€, and the flow verification device usually used air as the medium for negative pressure verification. In 1996, Huayang Metrology Substation was established. The station has mt primary standard equipment with a total uncertainty of 0.1% and a secondary standard device for the introduction of critical sonic nozzles from the US CEESI with a total uncertainty of 0.25% and natural gas flow. Real-flow verification conditions. In the recent 4 years, real-flow verification technology has matured, and a full set of natural gas flow verification methods, procedures, and management systems have been established, and are gradually close to foreign technologies such as the United States, the Netherlands, the United Kingdom, and Germany. In order to better simulate the on-site conditions, reduce the series of difficulties caused by loading and transportation, and control and reasonably reduce the on-site measurement errors, the actual flow verification in China gradually moves from the interior to the site. For example, the national crude oil flow metering station (Daqing) mobile sonic nozzle calibration vehicle (pressure 1.6MPa, diameter DN200mm, flow 90000m3/h), newly purchased mobile gas ultrasonic flow calibration vehicle (pressure 6.4MPa) , diameter DN600mm, service flow 80-8000 m3/h).
5. The gradual improvement and unification of standards
The orifice standard was upgraded from SYL04-83 to SY/T6143-1996 and is now being upgraded to the national standard. The "Using Gas Ultrasonic Flowmeter to Measure Natural Gas" non-equivalent uses AGA NO.9 and also references the ISO/TRl2765 section. Content, in April 2001, has passed the review of the national special committee. "Technical Requirements for Natural Gas Metering System", non-equivalent to PREN1776: "Basic Requirements for Natural Gas Measurement System". In August 2001, it has passed the review of the State Special Standards Committee. Preparations for the drafting of the National Standard for Measuring Natural Gas with Turbine Flowmeters are being prepared.
6. International traffic comparison
The overseas traffic comparison started earlier. In recent years, Huayang Meter Substation has conducted preliminary traffic comparisons with the United States CEESI, the United States SWRI, the Dutch NMI, and the German Pigsar. The results are basically consistent. In the 10th International Traffic Conference held in Brazil in 2000, China officially participated in the first meeting of the International Cyclical Comparison Working Group (BIFF/CIPM/CCM Subordinate Flow Measurement Working Group WGFF) as a member [3]. In early April 2001, China participated in the Second International Traffic Working Group (BIPM/CIPM/CCM/WGFF) meeting in Turkey.
7. Research Technology and International Academic Exchange Activities
In recent years, China's natural gas flow metering has made great achievements in scientific research. Typical scientific research projects include: "Natural gas, air, and water as the medium's influence on the orifice's metering performance", "Natural gas measurement technology research", "Gas ultrasonic flow meter testing and field application research," "New flow meter and Research and Application of New Rectifiers, "Study on Influencing Factors of Installation Conditions for Orifice Plates," etc.
China participates in international metrological academic activities more frequently, such as participating in API conferences in the United States, participating in the OMIL, hosting and bidding for the International Academic Meeting FLOMEKO and ISO/TC193. New Concept and Development Trend of Natural Gas Measurement
With China's accession to the WTO, the possibility of foreign-funded enterprises continuing to enter the natural gas market in China and the introduction of foreign natural gas, natural gas measurement and international standards will soon become a face-to-face reality [4], and its measurement concepts and development trends will also undergo a series of changes. The analysis shows that in the next step, China's natural gas measurement will develop in the following seven aspects:
l. Development of metering methods to automated, intelligent, remote metering methods
Due to the rapid development of electronic technologies, computers, and Internet technologies, natural gas metering has been gradually approaching online, real-time, and intelligent. At the same time, it is relying on network technology to achieve remote communications, control, and management, such as the application of SCADA systems and intelligent turbine flow meter intelligent systems.
2. Verification of verification methods and value tracking from static single parameter to dynamic multi-parameter traceability
In the past, the verification method of the flowmeter usually used the static single parameter method. For example, the standard orifice plate relies on the geometry verification method to verify the eight geometric static single parameters of the orifice plate to ensure the accuracy of the flowmeter. With the maturity of domestic and foreign real-flow verification technologies, the traceability of natural gas flow values ​​is gradually progressing toward real-flow verification, ie, sub-parameters such as pressure, temperature, and actual flow rate of the natural gas medium under conditions close to actual field conditions. The dynamic components of the temperament components and the total flow rate were traced.
3, instrument selection from a single instrument to the development of diversified instruments
In the past, the selection of flow meters was relatively simple. In recent years, with the research and development of flowmeters, different flowmeters have different characteristics and range of adaptability. Flow meter selection thus presents itself from a single meter to a diversified meter. For example, for the low pressure, medium and small flow can choose smart speed flowmeter (turbine, swirl into the vortex flowmeter); for high pressure, high flow rate can choose gas ultrasonic flowmeter. Recently, a new type of flowmeter, the Venturi tube, has emerged, which can be adapted to medium and low flow conditions with a wide range of flow rates.
4. Measurement standards evolve from a single standard to multiple standards
China's natural gas measurement standards have been continuously developed, enriched, and improved. After integrating foreign standards, China's flow metering standards have basically constituted a complete system and are gradually being developed from a single standard to multiple standards.
5, measurement methods from the volume measurement to the development of energy measurement
The measurement method of China's natural gas trade is measured by volume under the statutory quality index. With the continuous improvement of the market economy and the imminent accession of the WTO, China's natural gas trade measurement method should be brought into line with international standards as soon as possible. In May 2000, the 12th ISO/TC193 Annual Meeting was held in Chengdu. The paper discussed the SC2/WG4 working paper on natural gas energy measurement (ISO/WD 15112). In December 2000, it issued a committee file (ISO/CD 15112). ). With regard to the development of natural gas energy measurement, our country is speeding up the process and making corresponding preparations.
6, a single data management to the measurement system management development
Single data management has many shortcomings. The development of computer technology has created good conditions for the management of natural gas metering systems. The measurement management of natural gas carries out the whole process, dynamic and scientific management from all aspects and all aspects that affect the measurement results. The oil and gas measurement and information management system of Southwest Oil & Gas Field Branch, which is a research project to be completed by the Southwest Oil & Gas Field Branch of CNPC in 2001, provides an information management system for natural gas metering automation and process management.
7, measurement management after the implementation of measurement disputes explained to the prior process management development
With the development of market economy, people are paying more and more attention to natural gas measurement, especially trade measurement. Therefore, people are undergoing a fundamental shift in the concept of natural gas metering management, not only the use of on-site measurement instruments and the corresponding personnel management, but also engaged in the interpretation of post-measurement disputes to enhance pre-instrument procurement selection, installation, process control, quality Oversight, data management, real-flow verification management changes and development.
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